General characteristics of the giant planets. Giant planets - O'Five in physics! All giant planets have rapid axial rotation

Giant planets- the largest bodies in the Solar System after the Sun: Jupiter, Saturn, Uranus and Neptune. They are located beyond the Main Asteroid Belt and are therefore also called the “outer” planets.
Jupiter and Saturn are gas giants, meaning they consist mainly of gases that are in a solid state: hydrogen and helium.
But Uranus and Neptune were identified as ice giants, since in the thickness of the planets themselves, instead of metallic hydrogen, there is high-temperature ice.
Giant planets many times larger than the Earth, but compared to the Sun, they are not large at all:

Computer calculations have shown that giant planets play an important role in protecting the inner terrestrial planets from asteroids and comets.
Without these bodies in the solar system, our Earth would be hit by asteroids and comets hundreds of times more often!
How do giant planets protect us from the falls of uninvited guests?

You've probably heard about "space slalom", when automatic stations sent to distant objects in the solar system perform "gravitational maneuvers" near some planets. They approach them along a pre-calculated trajectory and, using the force of their gravity, accelerate even more, but do not fall onto the planet, but “shoot” the word from a sling at an even greater speed than at the entrance and continue their movement. This saves fuel, which would be needed for acceleration with engines alone.
In the same way, giant planets throw asteroids and comets outside the solar system, which fly past them, trying to break through to the inner planets, including the Earth. Jupiter, with its brothers, increases the speed of such an asteroid, pushes it out of its old orbit, it is forced to change its trajectory and flies into the cosmic abyss.
So, without giant planets, life on Earth would probably be impossible due to constant meteorite bombardment.

Well, now let’s briefly get acquainted with each of the giant planets.

Jupiter is the largest giant planet.

First in order from the Sun, among the giant planets, is Jupiter. It is also the largest planet in the solar system.
Sometimes they say that Jupiter is a failed star. But to start its own process of nuclear reactions, Jupiter does not have enough mass, and quite a lot. Although, the mass is slowly growing due to the absorption of interplanetary matter - comets, meteorites, dust and solar wind. One of the options for the development of the Solar system shows that if this continues, then Jupiter may well become a star or a brown dwarf. And then our Solar system will become a double star system. By the way, double star systems are a common occurrence in the Cosmos around us. There are much fewer single stars, like our Sun.

There are calculations showing that Jupiter is already emitting more energy than it absorbs from the Sun. And if this is really the case, then nuclear reactions must already be taking place, otherwise there is simply nowhere for the energy to come from. And this is a sign of a star, not a planet...


This image also shows the famous Great Red Spot, also called the “eye of Jupiter.” This is a giant vortex that has apparently existed for hundreds of years.

In 1989, the Galileo spacecraft was launched towards Jupiter. Over 8 years of work, he took unique photographs of the giant planet itself, the satellites of Jupiter, and also carried out many measurements.
One can only guess what is going on in the atmosphere of Jupiter and in its depths. The Galileo probe, having descended 157 km into its atmosphere, survived for only 57 minutes, after which it was crushed by a pressure of 23 atmospheres. But he managed to report powerful thunderstorms and hurricane winds, and also transmitted data on composition and temperature.
Ganymede, the largest of the moons of Jupiter, is also the largest of the moons of the planets in the Solar System.
At the very beginning of the research, in 1994, Galileo observed the fall of Comet Shoemaker-Levy onto the surface of Jupiter and sent back images of this disaster. This event could not be observed from Earth - only residual phenomena that became visible as Jupiter rotated.

Next comes an equally famous body of the solar system - the giant planet Saturn, which is known primarily for its rings. Saturn's rings are made up of ice particles ranging in size from dust grains to fairly large chunks of ice. With an outer diameter of 282,000 kilometers, Saturn's rings are only about ONE kilometer thick. Therefore, when viewed from the side, Saturn's rings are not visible.
But, Saturn also has satellites. About 62 satellites of Saturn have now been discovered.
Saturn's largest moon is Titan, which is larger than the planet Mercury! But, it consists largely of frozen gas, that is, it is lighter than Mercury. If Titan is moved into Mercury's orbit, the icy gas will evaporate and Titan's size will greatly decrease.
Another interesting satellite of Saturn, Enceladus, attracts scientists because there is an ocean of liquid water under its icy surface. And if so, then life is possible in it, because the temperatures there are positive. Powerful water geysers have been discovered on Enceladus, shooting hundreds of kilometers high!

The Cassini research station has been orbiting Saturn since 2004. During this time, a lot of data was collected about Saturn itself, its moons and rings.
The automatic station "Huygens" was also landed on the surface of Titan, one of Saturn's moons. This was the first ever landing of a probe on the surface of a celestial body in the Outer Solar System.
Despite its considerable size and mass, the density of Saturn is approximately 9.1 times less than the density of the Earth. Therefore, the acceleration of gravity at the equator is only 10.44 m/s². That is, having landed there, we would not have felt the increased gravity.

Uranus is an ice giant.

The atmosphere of Uranus consists of hydrogen and helium, and the interior is made of ice and solid rocks. Uranus appears to be a fairly calm planet, unlike the violent Jupiter, but vortices have still been noticed in its atmosphere. If Jupiter and Saturn are called gas giants, then Uranus and Neptune are ice giants, since in their depths there is no metallic hydrogen, but instead there is a lot of ice in various high-temperature states.
Uranus emits very little internal heat and is therefore the coldest of the planets in the solar system - a temperature of -224°C is recorded on it. Even on Neptune, which is further from the Sun, it is warmer.
Uranus has satellites, but they are not very large. The largest of them, Titania, is more than half the diameter of our Moon.

No, I didn't forget to rotate the photo :)

Unlike other planets in the solar system, Uranus seems to lie on its side - its own axis of rotation lies almost in the plane of rotation of Uranus around the Sun. Therefore, it turns to the Sun either with the South or North poles. That is, a sunny day at the pole lasts 42 years, and then gives way to 42 years of “polar night”, during which the opposite pole is illuminated.

This image was taken by the Hubble telescope in 2005. The rings of Uranus, the lightly colored south pole, and a bright cloud in the northern latitudes are visible.

It turns out that not only Saturn decorated himself with rings!

It is curious that all the planets bear the names of Roman gods. And only Uranus is named after a god from ancient Greek mythology.
The acceleration of gravity at the equator of Uranus is 0.886 g. That is, the gravity on this giant planet is even less than on Earth! And this despite its enormous mass... This is again due to the low density of the ice giant Uranus.

Spacecraft have flown past Uranus, taking pictures along the way, but detailed studies have not yet been carried out. True, NASA plans to send a research station to Uranus in the 2020s. The European Space Agency also has plans.

Neptune is the farthest planet in the solar system, after Pluto was "demoted" to the "dwarf planets". Like the other giant planets, Neptune is much larger and heavier than Earth.
Neptune, like Saturn, is an icy giant planet.

Neptune is quite far from the Sun and therefore became the first planet discovered through mathematical calculations, and not through direct observations. The planet was visually discovered through a telescope on September 23, 1846 by astronomers at the Berlin Observatory, based on preliminary calculations by the French astronomer Le Verrier.
It is curious that, judging by the drawings, Galileo Galii observed Neptune long before this, back in 1612, with his first telescope! But... he did not recognize it as a planet, mistaking it for a fixed star. Therefore, Galileo is not considered the discoverer of the planet Neptune.

Despite its significant size and mass, Neptune's density is approximately 3.5 times less than the density of Earth. Therefore, at the equator the gravity is only 1.14 g, that is, almost the same as on Earth, like the two previous giant planets.

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19. Giant planets

1. Features of the giant planets

Of the four giant planets, Jupiter is the best studied - the largest planet in this group and the closest of the giant planets to us and the Sun. Jupiter's rotation axis is almost perpendicular to the plane of its orbit, so there are no seasonal changes in lighting conditions.

All giant planets rotate around their axis quite quickly and have low density. As a result, they are significantly compressed.

All giant planets are surrounded by powerful, extended atmospheres, and we only see clouds floating in them, elongated in stripes parallel to the equator due to their rapid rotation.

Using the data in Appendix V, calculate the linear and angular velocities of rotation at the equators of the Earth and Jupiter.

Bands of clouds are visible on Jupiter even with a weak telescope (see flyleaf). Jupiter rotates in zones - the closer to the poles, the slower. At the equator, the rotation period is 9 hours 50 minutes, and at middle latitudes it is several minutes longer. Other giant planets rotate in a similar way.

Since the giant planets are far from the Sun, their temperature (at least above their clouds) is very low: on Jupiter - 145 ° C, on Saturn - 180 ° C, on Uranus and Neptune even lower.

The atmospheres of the giant planets contain mainly molecular hydrogen, there is methane CH 4 and, apparently, a lot of helium, and ammonia NH 3 was also found in the atmosphere of Jupiter and Saturn. The absence of NH 3 bands in the spectra of more distant planets is explained by the fact that it froze out there. At low temperatures, ammonia condenses and is likely what makes up Jupiter's visible clouds.

The chemical composition of clouds on planets is very different. What are the general properties of these clouds? What processes underlie their formation on various planets?

Intense movements covering the cloudy and neighboring layers of the atmosphere are stable. In particular, such a stable atmospheric “vortex” is the famous Red Spot, observed on Jupiter for over 300 years.

The study of processes occurring in the atmospheres of various planets helps terrestrial meteorology and climatology.

Models of massive planets consisting of hydrogen and helium have been theoretically constructed. Calculations of a model of the internal structure of Jupiter show that as it approaches the center, hydrogen must successively pass through gaseous, gas-liquid and liquid phases. In the center of the planet, where temperatures can reach several thousand Kelvin, there is a liquid core consisting of metals, silicates and hydrogen in the metallic phase, which occurs at pressures of the order of 10 11 Pa. In 1975, the metallic phase of hydrogen was obtained experimentally on Earth, which confirms the validity of theoretical calculations of the internal structure of the giant planets.

Due to the presence of a magnetic field, Jupiter has radiation belts similar to those on Earth, but significantly superior to them. Its magnetosphere extends over millions of kilometers, encompassing its four largest satellites. Jupiter is a source of radio emission. Spacecraft recorded powerful flashes of lightning on it.

Of the remaining data on the planets, the peculiarity of the axial rotation of Uranus, which, like Venus, occurs in the direction opposite to the direction of rotation of all other planets, deserves mention. In addition, it rotates as if lying on its side, so during the year there is a significant change in the lighting conditions of the planet's surface.

The most distant planet, Pluto, is not a giant planet. This is a very small and poorly studied cold planet, the year on which lasts about 250 Earth years.

2. Moons and rings of planets

Mercury and Venus have no satellites. The Earth has one natural satellite - Moon. It is only 4 times smaller in diameter than the Earth. Pluto has only one satellite discovered - Charon, which is half the size of the planet itself. Mars has two satellites - Phobos And Deimos(Fig. 53). The remaining planets have many satellites, but they are immeasurably smaller than their planets. Almost every spacecraft flying near the giant planets discovers previously unknown small satellites. Thus, Uranus has recently discovered 8 more satellites.

Using the table (see Appendix V), find the planets that have the largest number of satellites.

The largest satellites are Titanium(satellite of Saturn) and Ganymede(third satellite of Jupiter). They are 1.5 times the diameter of the Moon and slightly larger than Mercury. Titan is the only moon with a thick atmosphere, which is mainly composed of nitrogen.

With the help of automatic interplanetary stations, it was possible to obtain clear photographs of the satellites of Mars and many satellites of the giant planets from close range. Numerous surface details are clearly visible on them: craters, cracks, individual irregularities. The satellites of Jupiter and more distant planets are covered with a layer of ice and dust tens of kilometers thick. On a satellite of Jupiter - And about Several active volcanoes were photographed. All satellites were covered with craters, mainly of impact (meteorite) origin, even as small as the satellites of Mars, about 20 km in size (see Fig. 53).

Many satellites, like the Moon, always face the same side towards their planet. Their stellar rotation periods are equal to their orbital periods around their planets.

The four largest satellites of Jupiter can be seen even with prism binoculars. Through a telescope, in a few hours it is possible to observe how the satellites move noticeably (Fig. 54), sometimes pass between Jupiter and Earth, and sometimes go beyond the disk of Jupiter or into its shadow. Observing the periodicity of these eclipses of satellites, Roemer in the 17th century. discovered that the speed of propagation of light is finite, and determined its numerical value.

Many of the planets' satellites are interesting because of their motion; For example, Phobos orbits Mars three times faster than the planet itself rotates around its axis. Therefore, for an observer on Mars, it rises in the west twice a day and twice completely changes all phases, sweeping across the sky to meet the daily rotation of the stars. The satellites of Mars are close to its surface. Phobos is located from the surface of Mars at a distance less than the diameter of the planet.

The distant moons of Jupiter and Saturn are very small, irregularly shaped, and some of them point in the opposite direction to the rotation of the planet itself. The orbital planes of Uranus' satellites are close to the plane of the planet's equator and, therefore, almost perpendicular to the plane of its orbit.

Giant planets are characterized by the presence of not only a large number of satellites, but also rings. However, from Earth, a telescope can only see a bright ring, no more than a few hundred meters thick, surrounding Saturn (see cover). It is located in the plane of Saturn's equator, which is inclined to the plane of its Orbit by 27°.

Therefore, during the 30-year revolution of Saturn around the Sun, its ring is visible to us either quite open, or exactly edge-on, when it cannot be seen even in large telescopes (Fig. 55). The width of this ring is several times greater than the diameter of the globe.

The Russian scientist A. A. Belopolsky (1854-1934), having studied the spectrum of the ring, confirmed the theoretical conclusion that Saturn’s ring should not be continuous, but consist of many small particles. From the spectrum, using the Doppler effect, he established that the inner parts of the ring rotate faster than the outer ones, in accordance with Kepler's III law.

Photographs transmitted by automatic stations launched towards Saturn showed that its ring consists of many hundreds of individual narrow “rings” separated by dark spaces. It is assumed that this structure of the rings is associated with the gravitational influence of the planet’s numerous satellites on the movement of particles of the substance forming the rings.

The system of Saturn's rings either arose from the destruction of a once existing satellite of the planet (for example, during its collision with another satellite or an asteroid), or represents the remnant of the material from which the satellites of Saturn were formed in the distant past and which, due to the tidal influence of the planet, could not " assemble" into separate satellites.

The satellites of Mars, distant and small satellites of the giant planets, apparently were asteroids that these planets captured with their gravity.

Very faint and thin rings around Uranus and Jupiter have recently been discovered. They are significantly inferior in brightness to the rings of Saturn. Their existence around large planets was predicted earlier by the Soviet scientist S.K. Vsekhsvyatsky.

When preparing for your story about the planets, use the data in Appendix V and follow this plan:

1. The group to which the planet belongs. Distinctive characteristics of this group.

2. Size and mass of the planet.

3. Distance of the planet from the Sun.

4. Periods of its rotation and circulation.

5. Characteristics of the atmosphere.

6. Temperature conditions.

7. Relief (for terrestrial planets.)

8. Number and characteristics of satellites.

Space has long attracted people's attention. Astronomers began studying the planets of the Solar System back in the Middle Ages, examining them through primitive telescopes. But a thorough classification and description of the structural features and movements of celestial bodies became possible only in the 20th century. With the advent of powerful equipment, state-of-the-art observatories and spacecraft, several previously unknown objects were discovered. Now every schoolchild can list all the planets of the solar system in order. A space probe has landed on almost all of them, and so far man has only visited the Moon.

What is the Solar System

The Universe is huge and includes many galaxies. Our Solar System is part of a galaxy containing more than 100 billion stars. But there are very few that are like the Sun. Basically, they are all red dwarfs, which are smaller in size and do not shine as brightly. Scientists have suggested that the solar system was formed after the emergence of the Sun. Its huge field of attraction captured a gas-dust cloud, from which, as a result of gradual cooling, particles of solid matter formed. Over time, celestial bodies were formed from them. It is believed that the Sun is now in the middle of its life path, so it, as well as all the celestial bodies dependent on it, will exist for several more billions of years. Near space has been studied by astronomers for a long time, and any person knows what planets of the solar system exist. Photos of them taken from space satellites can be found on the pages of various information resources devoted to this topic. All celestial bodies are held by the strong gravitational field of the Sun, which makes up more than 99% of the volume of the Solar System. Large celestial bodies rotate around the star and around its axis in one direction and in one plane, which is called the ecliptic plane.

Planets of the Solar System in order

In modern astronomy, it is customary to consider celestial bodies starting from the Sun. In the 20th century, a classification was created that includes 9 planets of the solar system. But recent space exploration and new discoveries have pushed scientists to revise many provisions in astronomy. And in 2006, at an international congress, due to its small size (a dwarf with a diameter not exceeding three thousand km), Pluto was excluded from the number of classical planets, and there were eight of them left. Now the structure of our solar system has taken on a symmetrical, slender appearance. It includes the four terrestrial planets: Mercury, Venus, Earth and Mars, then comes the asteroid belt, followed by the four giant planets: Jupiter, Saturn, Uranus and Neptune. On the outskirts of the solar system there is also a space that scientists call the Kuiper Belt. This is where Pluto is located. These places are still little studied due to their distance from the Sun.

Features of the terrestrial planets

What allows us to classify these celestial bodies as one group? Let us list the main characteristics of the inner planets:

• relatively small size;
• hard surface, high density and similar composition (oxygen, silicon, aluminum, iron, magnesium and other heavy elements);
• presence of atmosphere;
• identical structure: a core of iron with nickel impurities, a mantle consisting of silicates, and a crust of silicate rocks (except for Mercury - it has no crust);
• a small number of satellites - only 3 for four planets;
• rather weak magnetic field.

Features of the giant planets

As for the outer planets, or gas giants, they have the following similar characteristics:

• large sizes and weights;
• they do not have a solid surface and consist of gases, mainly helium and hydrogen (therefore they are also called gas giants);
• liquid core consisting of metallic hydrogen;
• high rotation speed;
• a strong magnetic field, which explains the unusual nature of many processes occurring on them;
• there are 98 satellites in this group, most of which belong to Jupiter;
• The most characteristic feature of gas giants is the presence of rings. All four planets have them, although they are not always noticeable.

The first planet is Mercury

It is located closest to the Sun. Therefore, from its surface the star appears three times larger than from the Earth. This also explains the strong temperature changes: from -180 to +430 degrees. Mercury moves very quickly in its orbit. Maybe that’s why it got such a name, because in Greek mythology Mercury is the messenger of the gods. There is practically no atmosphere here and the sky is always black, but the Sun shines very brightly. However, there are places at the poles where its rays never hit. This phenomenon can be explained by the tilt of the rotation axis. No water was found on the surface. This circumstance, as well as the abnormally high daytime temperature (as well as the low nighttime temperature) fully explain the fact of the absence of life on the planet.

Venus

If you study the planets of the solar system in order, then Venus comes second. People could observe it in the sky back in ancient times, but since it was shown only in the morning and evening, it was believed that these were 2 different objects. By the way, our Slavic ancestors called it Mertsana. It is the third brightest object in our solar system. People used to call it the morning and evening star, because it is best visible before sunrise and sunset. Venus and Earth are very similar in structure, composition, size and gravity. This planet moves very slowly around its axis, making a full revolution in 243.02 Earth days. Of course, conditions on Venus are very different from those on Earth. It is twice as close to the Sun, so it is very hot there. The high temperature is also explained by the fact that thick clouds of sulfuric acid and an atmosphere of carbon dioxide create a greenhouse effect on the planet. In addition, the pressure at the surface is 95 times greater than on Earth. Therefore, the first ship that visited Venus in the 70s of the 20th century stayed there for no more than an hour. Another peculiarity of the planet is that it rotates in the opposite direction compared to most planets. Astronomers still know nothing more about this celestial object.

Third planet from the Sun

The only place in the Solar System, and indeed in the entire Universe known to astronomers, where life exists is Earth. In the terrestrial group it has the largest size. What else are her

1. The highest gravity among the terrestrial planets.
2. Very strong magnetic field.
3. High density.
4. It is the only one among all the planets that has a hydrosphere, which contributed to the formation of life.
5. It has the largest satellite compared to its size, which stabilizes its tilt relative to the Sun and influences natural processes.

The planet Mars

This is one of the smallest planets in our Galaxy. If we consider the planets of the solar system in order, then Mars is the fourth from the Sun. Its atmosphere is very rarefied, and the pressure on the surface is almost 200 times less than on Earth. For the same reason, very strong temperature changes are observed. The planet Mars has been little studied, although it has long attracted the attention of people. According to scientists, this is the only celestial body on which life could exist. After all, in the past there was water on the surface of the planet. This conclusion can be drawn from the fact that there are large ice caps at the poles, and the surface is covered with many grooves, which could be dried up river beds. In addition, there are some minerals on Mars that can only be formed in the presence of water. Another feature of the fourth planet is the presence of two satellites. What makes them unusual is that Phobos gradually slows down its rotation and approaches the planet, while Deimos, on the contrary, moves away.

What is Jupiter famous for?

The fifth planet is the largest. The volume of Jupiter would fit 1300 Earths, and its mass is 317 times that of Earth. Like all gas giants, its structure is hydrogen-helium, reminiscent of the composition of stars. Jupiter is the most interesting planet, which has many characteristic features:

• it is the third brightest celestial body after the Moon and Venus;
• Jupiter has the strongest magnetic field of any planet;
• it completes a full revolution around its axis in just 10 Earth hours - faster than other planets;
• An interesting feature of Jupiter is the large red spot - this is how an atmospheric vortex rotating counterclockwise is visible from Earth;
• like all giant planets, it has rings, although not as bright as Saturn’s;
• this planet has the largest number of satellites. He has 63 of them. The most famous are Europa, on which water was found, Ganymede - the largest satellite of the planet Jupiter, as well as Io and Calisto;
• Another feature of the planet is that in the shadow the surface temperature is higher than in places illuminated by the Sun.

Planet Saturn

It is the second largest gas giant, also named after the ancient god. It is composed of hydrogen and helium, but traces of methane, ammonia and water have been found on its surface. Scientists have found that Saturn is the rarest planet. Its density is less than that of water. This gas giant rotates very quickly - it makes one revolution in 10 Earth hours, as a result of which the planet is flattened from the sides. Huge speeds on Saturn and the wind - up to 2000 kilometers per hour. This is faster than the speed of sound. Saturn has another distinctive feature - it holds 60 satellites in its field of gravity. The largest of them, Titan, is the second largest in the entire solar system. The uniqueness of this object lies in the fact that by examining its surface, scientists for the first time discovered a celestial body with conditions similar to those that existed on Earth about 4 billion years ago. But the most important feature of Saturn is the presence of bright rings. They circle the planet around the equator and reflect more light than the planet itself. Four is the most amazing phenomenon in the solar system. What's unusual is that the inner rings move faster than the outer rings.

- Uranus

So, we continue to consider the planets of the solar system in order. The seventh planet from the Sun is Uranus. It is the coldest of all - the temperature drops to -224 °C. In addition, scientists did not find metallic hydrogen in its composition, but found modified ice. Therefore, Uranus is classified as a separate category of ice giants. An amazing feature of this celestial body is that it rotates while lying on its side. The change of seasons on the planet is also unusual: winter reigns there for as many as 42 Earth years, and the Sun does not appear at all; summer also lasts 42 years, and the Sun does not set during this time. In spring and autumn, the star appears every 9 hours. Like all giant planets, Uranus has rings and many satellites. As many as 13 rings revolve around it, but they are not as bright as those of Saturn, and the planet contains only 27 satellites. If we compare Uranus with the Earth, then it is 4 times larger than it, 14 times heavier and is located at a distance from the Sun of 19 times the path to the star from our planet.

Neptune: the invisible planet

After Pluto was excluded from the number of planets, Neptune became the last from the Sun in the system. It is located 30 times further from the star than the Earth, and is not visible from our planet even with a telescope. Scientists discovered it, so to speak, by accident: observing the peculiarities of the movement of the planets closest to it and their satellites, they concluded that there must be another large celestial body beyond the orbit of Uranus. After discovery and research, interesting features of this planet were revealed:

• due to the presence of a large amount of methane in the atmosphere, the color of the planet from space appears blue-green;
• Neptune's orbit is almost perfectly circular;
• the planet rotates very slowly - it makes one circle every 165 years;
• Neptune is 4 times larger than Earth and 17 times heavier, but the force of gravity is almost the same as on our planet;
• the largest of the 13 satellites of this giant is Triton. It is always turned to the planet with one side and slowly approaches it. Based on these signs, scientists suggested that it was captured by the gravity of Neptune.

There are about one hundred billion planets in the entire Milky Way galaxy. So far, scientists cannot study even some of them. But the number of planets in the solar system is known to almost all people on Earth. True, in the 21st century, interest in astronomy has faded a little, but even children know the names of the planets of the solar system.

PRESENTATION ON THE TOPIC: GIANT PLANETS compiled by: Rakhmanina T.

The giant planets rotate very quickly around their axes; It takes the huge Jupiter less than 10 hours to complete one revolution. Moreover, as it turned out as a result of ground-based optical observations, the equatorial zone of the giant planets rotates faster than the polar ones. The result of rapid rotation is a large compression of the giant planets. These planets are far from the Sun, and regardless of the nature of the seasons, low temperatures always prevail on them. There are no seasons at all on Jupiter, since the axis of this planet is almost perpendicular to the plane of its orbit.

Giant planets are distinguished by a large number of satellites; 16 of them have been discovered so far in St. Petersburg, 17 in Saturn, 16 in Uranus, and 8 only in Neptune. A remarkable feature of the giant planets is the rings, which are open on all planets. The most important feature of the structure of giant planets is that these planets do not have solid surfaces. On Jupiter, even in small telescopes, stripes stretched along the equator are visible. In the upper layers of the hydrogen-helium atmosphere of Jupiter, chemical compounds, hydrocarbons, and also various compounds are found in the form of impurities, which color the details of the atmosphere in red-brown and yellow colors.

The system of Jupiter's satellites resembles the solar system in miniature. The four moons discovered by Galileo are called the Galilean moons: IO, Europa, Ganymede and Callisto. The satellite closest to Jupiter, Amalthea, as well as all distant satellites located outside the orbits of the Galilean satellites, have an irregular shape and thus resemble the minor planets of the solar system.

Of Saturn's satellites, Titan, which has an atmosphere, is of particular interest. It consists almost entirely of nitrogen. Triton, Neptune’s largest satellite, is also remarkable. Triton's diameter is 2705 km. Triton has an atmosphere primarily composed of nitrogen. Triton is a silicate-ice celestial body; craters, polar caps, and even gas geysers have been discovered on it.

The rings of Saturn were the first to be discovered. Back in the 19th century, the English physicist J. Maxwell (1831-1879), who studied the stability of the motion of the rings of Saturn, as well as the Russian astrophysicist A.A. Belopolsky (1854-1934) proved that the rings of Saturn cannot be continuous. From Earth, through the best telescopes, several rings are visible, separated by intervals. The rings are very wide: they extend 60 thousand kilometers above the cloud layer of the planet. Each consists of particles and lumps moving in their orbits around Saturn. The thickness of the rings is no more than 1 km.

Therefore, when the Earth, during its movement around the Sun, finds itself in the plane of the rings of Saturn, the rings cease to be visible: it seems to us that they disappear. It is possible that the material from which the rings are composed was not included in the composition of the planets and their large satellites during the formation of these celestial bodies. Rings were discovered on Uranus in 1977, on Jupiter in 1979, and on Neptune in 1989. The possibility of the existence of rings on all giant planets was pointed out back in 1960 by the famous astronomer S.K. Vsekhsvyatsky.

Questions and tasks: 1. How do giant planets differ from terrestrial planets in their basic physical characteristics? 2. What is the peculiarity of the rotation of the giant planets around their axis? 3. What is the peculiarity of the structure of the giant planets? 4. What are planetary rings? 5. Why are Saturn’s rings sometimes not visible even with large telescopes? 6. What do you know about Jupiter and Saturn?

Thank you for your attention!!!

Our Solar System, if we mean its substance, consists of the Sun and four giant planets, and even more simply - of the Sun and Jupiter, since the mass of Jupiter is greater than all other circumsolar objects - planets, comets, asteroids - combined. In fact, we live in the Sun-Jupiter binary system, and all the other “trifles” are subject to their gravity

Saturn is four times smaller than Jupiter in mass, but is similar in composition: it also mainly consists of light elements - hydrogen and helium in a ratio of 9:1 in the number of atoms. Uranus and Neptune are even less massive and richer in composition in heavier elements - carbon, oxygen, nitrogen. Therefore, a group of four giants is usually divided in half into two subgroups. Jupiter and Saturn are called gas giants, and Uranus and Neptune are called ice giants. The fact is that Uranus and Neptune do not have a very thick atmosphere, and most of their volume is an icy mantle; i.e., a fairly solid substance. And Jupiter and Saturn have almost the entire volume occupied by a gaseous and liquid “atmosphere”. Moreover, all giants have iron-stone cores that exceed our Earth in mass.

At first glance, giant planets are primitive, while small planets are much more interesting. But maybe this is because we still do not know well the nature of these four giants, and not because they are of little interest. We just don't know them well. For example, in the entire history of astronomy, two ice giants - Uranus and Neptune - were approached only once by a space probe (Voyager 2, NASA, 1986 and 1989), and even then it flew past them without stopping. How much could he see and measure there? We can say that we have not yet really begun to study the ice giants.

The gas giants have been studied in much more detail, since in addition to the flyby vehicles (Pioneer 10 and 11, Voyager 1 and 2, Ulysses, Cassini, New Horizons, NASA and ESA), artificial ones have been operating near them for a long time satellites: Galileo (NASA) in 1995-2003. and Juno (NASA) have explored Jupiter since 2016, and Cassini (NASA and ESA) in 2004-2017. studied Saturn.

Jupiter was explored most deeply, and in the literal sense: a probe was dropped into its atmosphere from the Galileo, which flew there at a speed of 48 km/s, opened a parachute and in 1 hour descended 156 km below the top edge of the clouds, where at an external pressure of 23 atm and a temperature of 153 °C, it stopped transmitting data, apparently due to overheating. During the descent trajectory, he measured many parameters of the atmosphere, including even its isotopic composition. This has significantly enriched not only planetary science, but also cosmology. After all, giant planets do not let go of matter; they forever preserve what they were born from; This is especially true for Jupiter. Its cloudy surface has a second escape velocity of 60 km/s; it is clear that not a single molecule will ever escape from there.

Therefore, we think that the isotopic composition of Jupiter, especially the composition of hydrogen, is characteristic of the very first stages of life, at least of the Solar System, and perhaps the Universe. And this is very important: the ratio of heavy and light isotopes of hydrogen tells us how the synthesis of chemical elements proceeded in the first minutes of the evolution of our Universe, and what physical conditions existed then.

Jupiter rotates rapidly, with a period of about 10 hours; and since the average density of the planet is low (1.3 g/cm3), the centrifugal force noticeably deformed its body. When looking at the planet, you will notice that it is compressed along the polar axis. The degree of compression of Jupiter, i.e. the relative difference between its equatorial and polar radii is ( R eq − R floor)/ R eq = 0.065. It is the average density of the planet (ρ ∝ M/R 3) and its daily period ( T) determine the shape of her body. As you know, a planet is a cosmic body in a state of hydrostatic equilibrium. At the pole of the planet, only the force of gravity acts ( GM/R 2), and at the equator it is counteracted by centrifugal force ( V 2 /R= 4π 2 R 2 /RT 2). Their ratio determines the shape of the planet, since the pressure in the center of the planet should not depend on the direction: the equatorial column of matter should weigh the same as the polar one. The ratio of these forces (4π 2 R/T 2)/(GM/R 2) ∝ 1/(M/R 3)T 2 ∝ 1/(ρ T 2). So, the lower the density and the length of the day, the more compressed the planet is. Let's check: the average density of Saturn is 0.7 g/cm 3, its rotation period is 11 hours, almost the same as that of Jupiter, and its compression is 0.098. Saturn is compressed one and a half times more than Jupiter, and this is easy to notice when observing the planets through a telescope: the compression of Saturn is striking.

The rapid rotation of the giant planets determines not only the shape of their body, and therefore the shape of their observed disk, but also its appearance: the cloudy surface of the giant planets has a zonal structure with stripes of different colors stretched along the equator. Gas flows move quickly, at speeds of many hundreds of kilometers per hour; their mutual displacement causes shear instability and, together with the Coriolis force, generates giant vortices. From afar, the Great Red Spot on Jupiter, the Great White Oval on Saturn, and the Great Dark Spot on Neptune are visible. The anticyclone Great Red Spot (GRS) on Jupiter is especially famous. Once upon a time, the BKP was twice the size of the current one; it was seen by Galileo’s contemporaries in their weak telescopes. Today the BCP has faded, but still this vortex has been living in the atmosphere of Jupiter for almost 400 years, since it covers a gigantic mass of gas. Its size is larger than the globe. Such a mass of gas, once swirling, will not stop soon. On our planet, cyclones live for about a week, and there they last for centuries.

Any movement dissipates energy, which means it requires a source. Each planet has two groups of energy sources - internal and external. From outside, a stream of solar radiation pours onto the planet and meteoroids fall. From the inside, the planet is warmed by the decay of radioactive elements and the gravitational compression of the planet itself (the Kelvin-Helmholtz mechanism). . Although we have already seen large objects falling on Jupiter, causing powerful explosions (Comet Shoemaker-Levy 9), estimates of the frequency of their impact show that the average flow of energy they bring is significantly less than that brought by sunlight. On the other hand, the role of internal energy sources is ambiguous. For terrestrial planets, consisting of heavy refractory elements, the only internal source of heat is radioactive decay, but its contribution is negligible compared to the heat from the Sun.

Giant planets have a significantly lower proportion of heavy elements, but they are more massive and easier to compress, which makes the release of gravitational energy their main source of heat. And since the giants are removed from the Sun, the internal source becomes a competitor to the external one: sometimes the planet heats itself more than the Sun heats it. Even Jupiter, the giant closest to the Sun, emits (in the infrared region of the spectrum) 60% more energy than it receives from the Sun. And the energy that Saturn emits into space is 2.5 times greater than that the planet receives from the Sun.

Gravitational energy is released both during the compression of the planet as a whole and during the differentiation of its interior, i.e., when denser matter descends to the center and more “buoyant” is displaced from there. Both effects are likely at work. For example, Jupiter in our era is decreasing by approximately 2 cm per year. And immediately after formation, it was twice as large, contracted faster, and was significantly warmer. In its surroundings, it then played the role of a small sun, as evidenced by the properties of its Galilean satellites: the closer they are to the planet, the denser they are and the less they contain volatile elements (like the planets themselves in the Solar System).

In addition to the compression of the planet as a whole, differentiation of the interior plays an important role in the gravitational source of energy. Matter is divided into dense and buoyant, and dense matter sinks, releasing its potential gravitational energy in the form of heat. Probably, first of all, this is condensation and the subsequent fall of helium drops through the floating layers of hydrogen, as well as phase transitions of hydrogen itself. But there may be more interesting phenomena: for example, the crystallization of carbon - a rain of diamonds (!), although it does not release very much energy, since there is little carbon.

The internal structure of giant planets has so far been studied only theoretically. We have little chance of directly penetrating into their depths, and seismological methods, i.e., acoustic sounding, have not yet been applied to them. Perhaps someday we will learn to illuminate them using neutrinos, but this is still a long way off.

Fortunately, the behavior of matter has already been well studied in laboratory conditions at the pressures and temperatures that prevail in the interiors of giant planets, which provides grounds for mathematical modeling of their interiors. There are methods for monitoring the adequacy of models of the internal structure of planets. Two physical fields, magnetic and gravitational, whose sources are located in the depths, enter the space surrounding the planet, where they can be measured by space probe instruments.

The structure of the magnetic field is affected by many distorting factors (near-planetary plasma, solar wind), but the gravitational field depends only on the density distribution inside the planet. The more a planet’s body differs from a spherically symmetrical one, the more complex its gravitational field, the more harmonics it contains, distinguishing it from a simple Newtonian one. GM/R 2 .

The instrument for measuring the gravitational field of distant planets, as a rule, is the space probe itself, or more precisely, its movement in the planet’s field. The further the probe is from the planet, the weaker in its motion the minor differences in the planet’s field from the spherically symmetrical one appear. Therefore, it is necessary to launch the probe as close to the planet as possible. To this end, the new Juno probe (NASA) has been operating near Jupiter since 2016. It flies in a polar orbit, which has never happened before. In a polar orbit, the higher harmonics of the gravitational field are more pronounced because the planet is compressed and the probe occasionally comes very close to the surface. This is what makes it possible to measure the higher harmonics of the expansion of the gravitational field. But for the same reason, the probe will soon finish its work: it flies through the densest regions of Jupiter’s radiation belts, and its equipment suffers greatly from this.

Jupiter's radiation belts are colossal. Under high pressure, hydrogen in the bowels of the planet metallizes: its electrons are generalized, lose contact with the nuclei, and liquid hydrogen becomes a conductor of electricity. The huge mass of the superconducting medium, rapid rotation and powerful convection - these three factors contribute to the generation of a magnetic field due to the dynamo effect. In a colossal magnetic field that captures charged particles flying from the Sun, monstrous radiation belts are formed. In their densest part lie the orbits of the inner Galilean satellites. Therefore, a person did not live even a day on the surface of Europa, and not even an hour on Io. It’s not easy for even a space robot to be there.

Ganymede and Callisto, which are more distant from Jupiter, are in this sense much safer for research. Therefore, it is there that Roscosmos plans to send a probe in the future. Although Europe with its subglacial ocean would be much more interesting.

The ice giants Uranus and Neptune appear to be intermediate between gas giants and terrestrial planets. Compared to Jupiter and Saturn, they have smaller size, mass, and central pressure, but their relatively high average densities indicate a higher proportion of CNO group elements. The extended and massive atmospheres of Uranus and Neptune are mostly hydrogen-helium. Beneath it is a watery mantle mixed with ammonia and methane, which is commonly called icy mantle. But planetary scientists usually call the chemical elements of the CNO group and their compounds (H 2 O, NH 3, CH 4, etc.) “ices,” and not their aggregate state. So the mantle may be mostly liquid. And underneath it lies a relatively small iron-stone core. Since the concentration of carbon in the depths of Uranus and Neptune is higher than that of Saturn and Jupiter, at the base of their icy mantle there may be a layer of liquid carbon in which crystals condense, i.e., diamonds, settling down.

Let me emphasize that the internal structure of the giant planets is being actively discussed, and there are still quite a lot of competing models. Each new measurement from space probes and each new result of laboratory simulations in high-pressure installations lead to a revision of these models. Let me remind you that direct measurement of the parameters of very shallow layers of the atmosphere and only near Jupiter was carried out only once by a probe dropped from Galileo (NASA). And everything else is indirect measurements and theoretical models.

The magnetic fields of Uranus and Neptune are weaker than those of the gas giants, but stronger than those of Earth. Although the field induction at the surface of Uranus and Neptune is approximately the same as at the surface of the Earth (fractions of a gauss), the volume, and therefore the magnetic moment, is much greater. The geometry of the magnetic field of the ice giants is very complex, far from the simple dipole shape characteristic of the Earth, Jupiter and Saturn. The likely reason is that a magnetic field is generated in a relatively thin electrically conductive layer of the mantle of Uranus and Neptune, where convection currents do not have a high degree of symmetry (since the thickness of the layer is much less than its radius).

Despite their external similarity, Uranus and Neptune cannot be called twins. This is evidenced by their different average densities (1.27 and 1.64 g/cm 3, respectively) and different rates of heat release in the depths. Although Uranus is one and a half times closer to the Sun than Neptune, and therefore receives 2.5 times more heat from it, it is cooler than Neptune. The fact is that Neptune emits even more heat in its depths than it receives from the Sun, while Uranus emits almost nothing. The heat flux from the interior of Uranus near its surface is only 0.042 ± 0.047 W/m2, which is even less than that of the Earth (0.075 W/m2). Uranus is the coldest planet in the solar system, although not the farthest from the sun. Is this related to his strange “sideways” spin? It's possible.

Now let's talk about planetary rings.

Everyone knows that the “ringed planet” is Saturn. But upon careful observation, it turns out that all giant planets have rings. They are difficult to notice from Earth. For example, we do not see the ring of Jupiter through a telescope, but we notice it in backlight when the space probe looks at the planet from its night side. This ring consists of dark and very small particles, the size of which is comparable to the wavelength of light. They practically do not reflect light, but scatter it forward well. Uranus and Neptune are surrounded by thin rings.

In general, no two planets have identical rings; they are all different.

You can jokingly say that the Earth also has a ring. Artificial. It consists of several hundred satellites launched into geostationary orbit. This picture shows not only geostationary satellites, but also those in low orbits as well as those in high elliptical orbits. But the geostationary ring stands out quite noticeably against their background. However, this is a drawing, not a photo. No one has yet succeeded in photographing the artificial ring of the Earth. After all, its total mass is small, and its reflective surface is negligible. It is unlikely that the total mass of the satellites in the ring will be 1000 tons, which is equivalent to an asteroid 10 m in size. Compare this with the parameters of the rings of the giant planets.

It is quite difficult to notice any relationship between the parameters of the rings. The material of Saturn's rings is white as snow (albedo 60%), and the remaining rings are blacker than coal (A = 2-3%). All rings are thin, but Jupiter's is quite thick. Everything is made of cobblestones, but Jupiter is made of dust particles. The structure of the rings is also different: some resemble a gramophone record (Saturn), others resemble a matryoshka-shaped pile of hoops (Uranus), others are blurry, diffuse (Jupiter), and the rings of Neptune are not closed at all and look like arches.

I can’t wrap my head around the relatively small thickness of the rings: with a diameter of hundreds of thousands of kilometers, their thickness is measured in tens of meters. We have never held such delicate objects in our hands. If we compare the ring of Saturn with a sheet of writing paper, then with its known thickness the sheet would be the size of a football field!

As we see, the rings of all planets differ in the composition of particles, in their distribution, in morphology - each giant planet has its own unique decoration, the origin of which we do not yet understand. Typically, the rings lie in the equatorial plane of the planet and rotate in the same direction as the planet itself and the group of satellites close to it rotate. In earlier times, astronomers believed that the rings were eternal, that they existed from the moment the planet was born and would remain with it forever. Now the point of view has changed. But calculations show that the rings are not very durable, that their particles are slowed down and fall onto the planet, evaporate and scatter in space, and settle on the surface of satellites. So the decoration is temporary, although long-lived. Astronomers now believe that the ring is the result of a collision or tidal disruption of the planet's satellites. Perhaps Saturn's ring is the youngest, which is why it is so massive and rich in volatiles (snow).

And so a good telescope with a good camera can take pictures. But here we still don’t see almost any structure in the ring. A dark “gap” has long been noticed - the Cassini gap, which was discovered more than 300 years ago by the Italian astronomer Giovanni Cassini. There seems to be nothing in the gap.

The plane of the ring coincides with the equator of the planet. It cannot be otherwise, since a symmetrical oblate planet has a potential hole in the gravitational field along the equator. In a series of images taken from 2004 to 2009, we see Saturn and its ring from different angles, since Saturn's equator is inclined to the plane of its orbit by 27°, and the Earth is always close to this plane. In 2004, we were definitely in the plane of the rings. You understand that with a thickness of several tens of meters, we cannot see the ring itself. Nevertheless, the black stripe on the planet’s disk is noticeable. This is the shadow of a ring on the clouds. It is visible to us because the Earth and the Sun look at Saturn from different directions: we look exactly in the plane of the ring, but the Sun illuminates from a slightly different angle and the shadow of the ring falls on the cloudy layer of the planet. If there is a shadow, it means there is quite densely packed substance in the ring. The shadow of the ring disappears only on the equinoxes on Saturn, when the Sun is exactly in its plane; and this independently indicates the small thickness of the ring.

Many works have been devoted to the rings of Saturn. James Clerk Maxwell, the same one who became famous for his equations of the electromagnetic field, investigated the physics of the ring and showed that it could not be a single solid object, but must consist of small particles, otherwise the centrifugal force would tear it apart. Each particle flies in its own orbit - the closer to the planet, the faster.

Looking at any subject from a different perspective is always useful. Where in direct light we saw blackness, a “dip” in the ring, here we see matter; it’s just a different type, reflects and scatters light differently

When space probes sent us pictures of Saturn's ring, we were amazed by its fine structure. But back in the 19th century, outstanding observers at the Pic du Midi Observatory in France saw exactly this structure with their eyes, but no one really believed them then, because no one except them noticed such subtleties. But it turned out that Saturn’s ring is just like that. Stellar dynamics experts are looking for an explanation for this fine radial structure of the ring in terms of the resonant interaction of ring particles with Saturn’s massive satellites outside the ring and small satellites inside the ring. In general, the theory of density waves copes with the task, but it is still far from explaining all the details.

The top photo shows the day side of the ring. The probe flies through the plane of the ring, and we see in the bottom photo how it turned to us with its night side. The material in the Cassini division became quite visible from the shadow side, and the bright part of the ring, on the contrary, darkened, since it is dense and opaque. Where there was blackness, brightness appears because small particles do not reflect, but scatter light forward. These images show that matter is everywhere, just particles of different sizes and structures. We don’t yet really understand what physical phenomena separate these particles. The top image shows Janus, one of Saturn's moons.

It must be said that although spacecraft flew close to the ring of Saturn, none of them managed to see the real particles that make up the ring. We see only their general distribution. It is not possible to see individual blocks; they do not risk launching the apparatus into the ring. But someday it will have to be done.

From the night side of Saturn, those faintly visible parts of the rings immediately appear that are not visible in direct light.

This is not a true color photograph. The colors here show the characteristic size of the particles that make up a particular area. Red are small particles, turquoise are larger.

At that time, when the ring turned edge-on towards the Sun, shadows from large inhomogeneities fell on the plane of the ring (top photo). The longest shadow here is from the satellite Mimas, and numerous small peaks, which are shown in the enlarged image in the inset, have not yet received a clear explanation. Kilometer-sized protrusions are responsible for them. It is possible that some of them are shadows from the largest stones. But the quasi-regular structure of the shadows (photo below) is more consistent with temporary accumulations of particles resulting from gravitational instability.

Satellites fly along some of the rings, the so-called “watchdogs” or “herding dogs”, which with their gravity keep some of the rings from blurring. Moreover, the satellites themselves are quite interesting. One moves inside a thin ring, the other outside (for example, Janus and Epimetheus). Their orbital periods are slightly different. The inner one is closer to the planet and, therefore, orbits it faster, catches up with the outer satellite and, due to mutual attraction, changes its energy: the outer one slows down, the inner one accelerates, and they change orbits - the one that slowed down goes into a low orbit, and the one that accelerated goes into a low orbit. to high. So they make several thousand revolutions, and then change places again. For example, Janus and Epimetheus change places every 4 years.

A few years ago, the most distant ring of Saturn was discovered, which was not suspected at all. This ring is connected to the moon Phoebe, from whose surface dust flies off, filling the area along the satellite's orbit. The plane of rotation of this ring, like the satellite itself, is not connected with the equator of the planet, since due to the great distance, Saturn’s gravity is perceived as the field of a point object.

Each giant planet has a family of satellites. Jupiter and Saturn are especially rich in them. Today, Jupiter has 69 of them, and Saturn has 62, and new ones are being discovered regularly. The lower limit of mass and size for satellites has not been formally established, so for Saturn this number is arbitrary: if an object 20-30 meters in size is discovered near the planet, then what is it - a satellite of the planet or a particle of its ring?

In any large family of cosmic bodies, there are always more small ones than large ones. Planetary satellites are no exception. Small satellites are, as a rule, irregularly shaped blocks, mainly consisting of ice. Having a size of less than 500 km, they are not able to give themselves a spheroidal shape with their gravity. Outwardly, they are very similar to asteroids and comet nuclei. Probably, many of them are such, since they move far from the planet in very chaotic orbits. The planet could capture them, and after a while it could lose them.

We are not yet very familiar with small asteroid-like satellites. Such objects near Mars have been studied in more detail than others - its two small satellites, Phobos and Deimos. Particularly close attention was paid to Phobos; They even wanted to send a probe to its surface, but it hasn’t worked out yet. The more closely you look at any cosmic body, the more mysteries it contains. Phobos is no exception. Look at the strange structures that run along its surface. Several physical theories already exist that try to explain their formation. These lines of small dips and furrows are similar to meridians. But no one has yet proposed a physical theory of their formation.

All small satellites bear numerous traces of impacts. From time to time they collide with each other and with bodies coming from afar, split into separate parts, and may even unite. Therefore, reconstructing their distant past and origins will not be easy. But among the satellites there are also those that are genetically related to the planet, since they move next to it in the plane of its equator and, most likely, have a common origin with it.

Of particular interest are large planet-like satellites. Jupiter has four of them; these are the so-called “Galilean” satellites - Io, Europa, Ganymede and Callisto. The mighty Titan stands out from Saturn for its size and mass. These satellites are almost indistinguishable from planets in their internal parameters. It’s just that their movement around the Sun is controlled by even more massive bodies - the mother planets.

Here in front of us are the Earth and the Moon, and next to us, on a scale, is Saturn’s satellite Titan. A wonderful little planet with a dense atmosphere, with large liquid "seas" of methane, ethane and propane on the surface. Seas of liquefied gas, which at the surface temperature of Titan (–180 °C) are in liquid form. A very attractive planet, because it will be easy and interesting to work on - the atmosphere is dense, reliably protects from cosmic rays and is close in composition to the earth’s atmosphere, since it also mainly consists of nitrogen, although it is devoid of oxygen. Vacuum suits are not needed there, since the atmospheric pressure is almost the same as on Earth, even a little more. Dress warmly, have an oxygen canister on your back, and you will easily work on Titan. By the way, this is the only satellite (besides the Moon) on the surface of which it was possible to land a spacecraft. It was Huygens, carried there aboard Cassini (NASA, ESA), and the landing was quite successful.

Here is the only photo taken on the surface of Titan. The temperature is low, so the blocks are very cold water ice. We are sure of this because Titan generally consists mostly of water ice. The color is reddish-reddish; it is natural and is due to the fact that in the atmosphere of Titan, under the influence of solar ultraviolet radiation, quite complex organic substances are synthesized under the general name “tholins”. The haze of these substances transmits mainly orange and red colors to the surface, scattering them quite strongly. Therefore, studying the geography of Titan from space is quite difficult. Radar helps. In this sense, the situation resembles Venus. By the way, the atmospheric circulation on Titan is also of the Venusian type: one powerful cyclone in each hemisphere.

The satellites of other giant planets are also original. This is Io, the closest satellite of Jupiter. It is at the same distance as the Moon from the Earth, but Jupiter is a giant, which means it acts very strongly on its satellite. Jupiter's interior melted and on it we see many active volcanoes (black dots). It can be seen that around volcanoes the emissions follow ballistic trajectories. After all, there is practically no atmosphere there, so what is thrown out of the volcano flies in a parabola (or in an ellipse?). The low gravity on Io's surface creates conditions for high emissions: 250-300 km up, or even straight into space!

The second satellite from Jupiter is Europa. Covered with ice crust, like our Antarctica. Beneath the crust, which is estimated to be 25-30 km thick, is an ocean of liquid water. The ice surface is covered with numerous ancient cracks. But under the influence of the subglacial ocean, layers of ice slowly move, reminiscent of the drift of the earth's continents.

Cracks in the ice open from time to time, and water rushes out in fountains. Now we know this for sure, because we saw the fountains using the Hubble Space Telescope. This opens up the prospect of exploring the waters of Europe. We already know something about it: it is salt water, a good conductor of electricity, as indicated by the magnetic field. Its temperature is probably close to room temperature, but we still know nothing about its biological composition. I would like to scoop up and analyze this water. And expeditions for this purpose are already being prepared.

Other large satellites of the planets, including our Moon, are no less interesting. In fact, they represent an independent group of satellite planets.

Here, on the same scale, the largest satellites are shown in comparison with Mercury. They are in no way inferior to him, and by their nature some of them are even more interesting.